Diamond anode

Abstract

According to one aspect of the invention a robust anode structure and methods of making and using said structure to produce ionizing radiation are disclosed. An ionizing radiation producing layer is bonded to the target side of a highly conductive diamond substrate, by a metal carbide layer. The metal carbide layers improves the strength and durability of the bond, thus improving heat removal from the anode surface and reducing the risk of delaminating the ionizing radiation producing layer, thus reducing degradation and extending the anode's life. A smoothing dopant is alloyed into the radiation producing layer to facilitate keeping the layer surface smooth, thus improving the quality of the x-ray beam emitted from the anode. In an embodiment, the heat sink comprises a metal carbide skeleton cemented diamond material. In another embodiment, the heat sink is bonded to the diamond substrate structure in a high temperature reactive brazing process.

1. An anode for generating ionizing radiation comprising:
 a diamond substrate, having a target side and a backside, and having a thermal conductivity higher than aluminum; 
 a metal carbide layer on the target side of the diamond substrate; and 
 an ionizing radiation producing layer over the metal carbide layer. 
 
     
     
       2. The anode as claimed in  claim 1 , wherein the metal carbide layer is thick enough to inhibit delamination of the ionizing radiation producing layer, but not so thick as to unduly increase the thermal resistance to the diamond substrate, wherein said unduly increase in thermal resistance would result in a large enough build up of heat to raise the temperature of the radiation producing layer to cause the radiation producing layer to melt, vaporize, and/or delaminate. 
     
     
       3. The anode as claimed in  claim 1 , further comprising a buffer layer between the metal carbide layer and the ionizing radiation producing layer;
 wherein the buffer layer comprises a metal carbide forming material. 
 
     
     
       4. The anode as claimed in  claim 1 , wherein the ionizing radiation producing layer is selected from the group consisting of aluminum, magnesium, tungsten, and any combination thereof. 
     
     
       5. The anode as claimed in  claim 1 , wherein the metal carbide layer is selected from the group consisting of chromium carbide, titanium carbide, iron carbide, silicon carbide, germanium carbide, gold carbide, boron carbide, iridium carbide, lanthanum carbide, lithium carbide, manganese carbide, molybdenum carbide, osmium carbide, rhenium carbide, rhodium carbide, ruthenium carbide, thorium carbide, uranium carbide, vanadium carbide, tungsten carbide, and any combination thereof. 
     
     
       6. The anode as claimed in  claim 5 , wherein the thickness of the metal carbide layer is between about 2 nm. and about 200 nm. 
     
     
       7. The anode as claimed in  claim 1 , wherein the ionizing radiation producing layer further comprises a surface smoothing dopant. 
     
     
       8. The anode as claimed in  claim 7 , wherein the surface smoothing dopant is selected from the group consisting of copper, tungsten, titanium, nickel, gold, and chromium. 
     
     
       9. The anode as claimed in  claim 7 , wherein the concentration of the surface smoothing dopant is sufficiently high enough to inhibit surface roughening, without substantially reducing the intensity of the ionizing radiation emitted from the anode when irradiated with energized electrons. 
     
     
       10. The anode as claimed in  claim 7 , wherein the concentration of the surface smoothing dopant is between about 10 wt. % and about 0.01 wt. %. 
     
     
       11. The anode as claimed in  claim 1 , further comprising a heat sink bonded to the backside of the diamond substrate. 
     
     
       12. The anode as claimed in  claim 11 , wherein the means for bonding further comprises:
 a backside metal carbide layer on the backside of the diamond substrate; and 
 one or more backside layers between the backside metal carbide layer and the heat sink; 
 wherein, the backside metal carbide layer bonds to the diamond substrate and to the backside layer, which is attached to the heat sink. 
 
     
     
       13. The anode as claimed in  claim 12 , wherein the one or more backside layers are selected from the group consisting of titanium, chromium, nickel, gold, silver, aluminum, copper, any alloy thereof, and any combination thereof. 
     
     
       14. The anode as claimed in  claim 12 , wherein the means for bonding further comprises a solder layer between the backside layers and heat sink;
 wherein the solder layer comprises a low melting temperature material that when heated to soldering temperatures would not cause undue oxidation of the ionizing radiation forming layer. 
 
     
     
       15. The anode as claimed in  claim 14 , wherein the low melting temperature material has a working soldering temperature of less than or about 280° C. 
     
     
       16. The anode as claimed in  claim 14 , wherein the solder layer is selected from the group consisting of an alloy of gold and tin, an alloy of silver and tin, an alloy of lead and tin, an alloy of silver and lead, and any combination thereof. 
     
     
       17. The anode as claimed in  claim 16 , wherein the solder layer is compose of an alloy of gold and tin, containing approximately 10% to 30% tin and approximately 90% to 70% gold. 
     
     
       18. The anode as claimed in  claim 12 , wherein the backside layers comprise:
 a backside chromium layer attached to the backside carbide layer; 
 a backside nickel layer attached to the backside chromium layer; and 
 a backside gold layer attached to the backside nickel layer. 
 
     
     
       19. The anode as claimed in  claim 11 , wherein the heat sink comprises a high thermal conductivity material;
 wherein the high thermal conductivity material is selected from the group consisting of skeleton cemented diamond (ScD), BeO, tungsten, silicon carbide, aluminum nitride, copper, aluminum, silver, and any combination thereof; 
 wherein the skeleton cemented diamond comprises diamond grains within a binding matrix of one or more hard ceramics having very high melting points. 
 
     
     
       20. The anode as claimed in  claim 19 , wherein the heat sink comprises one or more channels within the body of the heat sink, in which cooling fluids can flow through the channels and remove heat from the heat sink. 
     
     
       21. The anode as claimed in  claim 20 , wherein the channels further comprise a conductive foam within the channels to further increase the total effective surface area of the channels without significantly reducing the flow rate of the cooling fluid. 
     
     
       22. A method of making an anode for generating radiation comprising the steps of:
 obtaining a diamond substrate, having a high conductivity, and having a target side and a backside; 
 forming a metal carbide layer on the target side of the diamond substrate; and 
 forming a radiation producing layer over the metal carbide layer. 
 
     
     
       23. The method of making an anode as claimed in  claim 22 , further comprising the step of forming an initial buffer layer on the target side of the diamond substrate;
 wherein the step of forming the initial buffer layer occurs before the formation of the radiation producing layer; and 
 wherein the initial buffer layer comprises a carbide forming material. 
 
     
     
       24. The method of making an anode as claimed in  claim 23 , wherein the initial buffer layer thickness is less than about 100 nm. 
     
     
       25. The method of making an anode as claimed in  claim 23 , further comprising the step of a carbide anneal after the formation of the buffer layer and before the formation of the x-ray producing layer;
 wherein the carbide anneal step produces a metal carbide layer on the diamond substrate; 
 wherein the initial buffer layer is consumed by the formation of the metal carbide layer. 
 
     
     
       26. The method of making an anode as claimed in  claim 25 , wherein the anneal comprises a vacuum anneal;
 wherein the vacuum anneal is performed under vacuum, at a temperature between about 300° C. and about 600° C. 
 
     
     
       27. The method of making an anode as claimed in  claim 25 , wherein the vacuum anneal comprises a laser anneal. 
     
     
       28. The method of making an anode as claimed in  claim 22 , wherein the step of forming the carbide layer, further comprise the steps of:
 performing a wafer surface clean; and 
 depositing the metal carbide layer by means of a chemical vapor deposition (CVD). 
 
     
     
       29. The method of making an anode as claimed in  claim 28 , wherein the step of performing a wafer surface clean, further comprise the steps of:
 degassing the substrate by heating the substrate to between about 100° C. and about 200° C.; and 
 sputter cleaning for a duration of between about 2 min. to about 30 min., at a power level between 100 Watts and 700 Watts. 
 
     
     
       30. The method of making an anode as claimed in  claim 22 , wherein the step of forming the carbide layer further comprise the steps of:
 implanting one or more carbide forming materials into the target side of the diamond wafer; and 
 vacuum annealing the diamond substrate to form the carbide layer. 
 
     
     
       31. The method of making an anode as claimed in  claim 22 , further comprising the step of bonding a heat sink to the backside of the diamond substrate;
 wherein the means of bonding the heat sink comprises; 
 forming a backside layer attached to the backside of the diamond substrate; 
 annealing to form a backside carbide layer on the backside of the diamond substrate. 
 
     
     
       32. The method of making an anode as claimed in  claim 31 , further comprising the formation of one or more backside layers over the backside carbide layer,
 wherein the means for attaching further comprises bonding the heat sink to the one or more backside layers by forming a solder layer. 
 
     
     
       33. The method of making an anode as claimed in  claim 32 , wherein forming of the solder layer comprises placing a foil of solder between the heat sink and the diamond substrate structure, thus forming a solder sandwich; and further comprising:
 heating the solder sandwich, to soldering temperatures; and 
 preventing the oxidation of the target side surface of the structure, by heating either under vacuum or in a forming gas environment. 
 
     
     
       34. The method of making an anode as claimed in  claim 32 , wherein forming of the solder layer comprises
 depositing a solder layer on the backside layers and/or on the heat sink; and further comprising: 
 placing the heat sink and the backside layers together, having the solder layer interposed in between, thus forming a solder sandwich; 
 heating the solder sandwich, to soldering temperatures, either in a vacuum or in a foaming environment; and 
 cooling the solder sandwich to below soldering temperatures, while the heat sink and the back side layers are still in contact with each other. 
 
     
     
       35. The method of making an anode as claimed in  claim 32 , wherein the solder layer comprising an alloy having concentrations approximately corresponding to a eutectic melting point. 
     
     
       36. The method of making an anode as claimed in  claim 35 , wherein the alloy having concentrations approximately corresponding to a eutectic melting point comprises an alloy of approximately 80% gold and approximately 20% tin. 
     
     
       37. The method of making an anode as claimed in  claim 22 , further comprising the steps of:
 cleaning the diamond substrate; 
 degassing the substrate by heating the diamond substrate to between about 100° C. and about 200° C.; 
 sputter cleaning the diamond substrate; 
 depositing one or more carbide forming materials into one or more bark side carbide forming layers on the backside of the diamond substrate; 
 degassing the substrate by heating the diamond substrate to between about 100° C. and about 200° C.; 
 sputter cleaning the substrate; 
 depositing one or more carbide forming materials into one or more target side carbide forming layers on the target side of the diamond substrate; 
 vacuum annealing the diamond substrate to form both a target side carbide layer and a backside carbide layer; 
 wherein the vacuum anneal is performed under vacuum, at a temperature between about 300° C. and about 600° C.; 
 degassing the substrate by heating the diamond substrate to between about 100° C. and about 200° C.; 
 sputter cleaning the substrate; 
 depositing the x-ray producing layer over the target side carbide layer; 
 wherein the x-ray producing layer is selected from the group consisting of aluminum, magnesium, and any combination thereof; 
 wherein the x-ray producing layer further comprises a surface smoothing material; 
 wherein the surface smoothing material comprises copper; 
 degassing the substrate by heating the substrate to between about 100° C. and about 200° C.; 
 sputter cleaning the substrate, under vacuum, for a duration of between about 2 min. to about 30 min., at a power level between 100 Watts and 700 Watts; 
 wherein both the degassing and sputter cleaning steps are under vacuum and at a low enough temperature to inhibit oxidation of the x-ray producing layer; 
 depositing one or more backside conductive layers to the backside carbide forming layers; 
 attaching a heat sink to the backside of the substrate; 
 wherein the means of attaching the heat sink comprises; 
 bonding the heat sink to the one or more backside conductive layers by means of a solder layer. 
 
     
     
       38. A method of using an anode for generating ionizing radiation comprising the step of:
 irradiating with energetic particles the surface of an ionizing radiation producing layer formed over a carbide layer on the target side of a diamond substrate so as to produce ionizing radiation from said surface of the ionizing radiation producing layer, 
 wherein the carbide layer bonds the ionizing radiation producing layer to the diamond substrate, and 
 wherein the diamond substrate has a high thermal conductivity and removes heat from the surface of the ionizing radiation producing layer to a heat sink attached to the backside of the diamond substrate. 
 
     
     
       39. The method of using an anode as claimed in  claim 38 , further comprising the step of:
 cooling said heat sink by passing coolant through channels formed within the heat sink. 
 
     
     
       40. The method of using an anode as claimed in  claim 39 , wherein the removal of heat from the heat sink by the coolant is further increased by the use of a conductive foam in the channels of said heat sink. 
     
     
       41. The method of using an anode as claimed in  claim 38 ,
 wherein the irradiating with energetic particles comprises an electron beam; and 
 wherein the producing of ionizing radiation comprises x-ray radiation. 
 
     
     
       42. The method of using an anode as claimed in  claim 38 , further comprising the step of:
 processing said ionizing radiation for use in an instrument, 
 wherein the instrument impinges energetic particles upon the anode to generate an emission of ionizing radiation onto a specimen, 
 wherein the surface of the ionizing radiation producing layer is maintained smoother by use of a surface smoothing dopant in the ionizing radiation producing layer. 
 
     
     
       43. The method of using an anode as claimed in  claim 42 , wherein the instrument is used for x-ray photoelectron spectroscopy. 
     
     
       44. An anode for generating ionizing radiation comprising:
 a diamond substrate, having a target side and a backside, and having a thermal conductivity higher than aluminum; 
 a metal carbide layer on the target side of the diamond substrate; 
 an ionizing radiation producing layer over the metal carbide layer; 
 a heat sink bonded to the backside of the diamond substrate; and 
 wherein the heat sink comprises a skeleton cemented diamond material. 
 
     
     
       45. The anode as claimed in  claim 44 , wherein the skeleton cemented diamond material comprises a metal carbide skeleton cemented diamond material. 
     
     
       46. The anode as claimed in  claim 45 , further comprising a metal carbide layer interposed between the diamond substrate and the heat sink. 
     
     
       47. The anode as claimed in  claim 45 , wherein the metal carbide skeleton cemented diamond material comprises silicon carbide. 
     
     
       48. The anode as claimed in  claim 45 , wherein the metal carbide skeleton cemented diamond material comprises a metal carbide cement mixed with a diamond material selected from the group consisting of diamond powder, diamond dust, diamond fragments, and any combination thereof. 
     
     
       49. A method of making an anode for generating radiation comprising:
 providing a diamond substrate, having a high conductivity, and having a target side and a backside; 
 providing a heat sink, having a high conductivity; 
 bonding together the diamond substrate and the heat sink by a high temperature reactive brazing process; 
 wherein the said high temperature reactive brazing process comprises:
 depositing a metal carbide forming layer between the diamond substrate and the heat sink; 
 heating the diamond substrate, the metal carbide forming layer, and the heat sink, to metal carbide forming temperatures; 
 sustaining said metal carbide forming temperatures until a metal carbide layer is formed between the heat sink and the diamond substrate; 
 
 forming a metal carbide layer on the target side of the diamond substrate; and 
 forming a radiation producing layer over the carbide layer. 
 
     
     
       50. The method of making an anode as claimed in  claim 49 , wherein the heat sink comprises a high thermal conductivity material;
 wherein the high thermal conductivity material is selected from the group consisting of skeleton cemented diamond (ScD), BeO, tungsten, silicon carbide, aluminum nitride, copper, aluminum, silver, and any combination thereof; wherein the skeleton cemented diamond comprises diamond grains within a binding matrix of one or more hard ceramics having very high melting points. 
 
     
     
       51. The method of making an anode as claimed in  claim 50 , wherein the heat sink comprises skeleton cemented diamond material;
 wherein the skeleton cemented diamond material comprises diamond grains within a binding matrix comprising a hard ceramic having very high melting point; 
 wherein, the diamond grains range in size from about 5 microns to about 250 microns; and 
 wherein, the diamond grains comprise about 30 to 70 volume percent of the skeleton cemented diamond. 
 
     
     
       52. The method of making an anode as claimed in  claim 50 , further comprising:
 forming a metal carbide forming layer on the target side of the diamond substrate; and 
 wherein the heating, at carbide forming temperatures, also forms the metal carbide layer on the target side of the diamond substrate, from the metal carbide forming layer.